Substrate processing apparatus, method of manufacturing semiconductor device and method of cleaning processing vessel

ABSTRACT

When a dry cleaning process is performed in a processing chamber by adding nitrogen monoxide (NO) gas to a cleaning gas, the handling is facilitated, and cleaning performance is improved. A substrate processing apparatus includes a processing vessel configured to process a substrate, a first cleaning gas supply system configured to pre-mix a gas containing fluorine atoms with the NO gas and supply the pre-mixed gas into the processing vessel, and a second cleaning gas supply system installed apart from the first cleaning gas supply system and configured to supply the fluorine-containing gas into the processing vessel.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to and the benefit of Japanese PatentApplication No. 2010-099984 filed on Apr. 23, 2010, the disclosure ofwhich is incorporated herein by reference.

1. FIELD OF THE INVENTION

The present invention relates to a substrate processing apparatus forprocessing a substrate, a method of manufacturing a semiconductor deviceincluding a process of processing a substrate and a method of cleaning aprocessing vessel.

2. BACKGROUND

A thin-film forming process for forming a CVD thin film such as thesilicon nitride film (a Si₃N₄ film) on a substrate such as asemiconductor wafer using a thermal chemical vapor deposition (“CVD”)technique is one of processes of manufacturing a semiconductor device.The thin-film forming process using thermal CVD technique is performedby supplying a processing gas into a processing chamber having thesubstrate loaded therein. While the thin-film forming process is aimedat forming the thin film on a surface of the substrate, an undesirabledeposit including the thin film is also adhered to regions other thanthe surface of the substrate, for example, to an inner wall of areaction tube constituting the processing chamber. The deposit isaccumulatively adhered each time the thin-film forming process isperformed, and delaminated when the deposit reaches a predeterminedthickness or more, thereby generating foreign matters (particles) in theprocessing chamber. Accordingly, whenever the deposit reaches thepredetermined thickness, it is necessary to clean the inside of theprocessing chamber and members disposed in the processing chamber byremoving the deposit.

The configuration of the typical CVD thin-film forming apparatus for asemiconductor will be described with reference to FIG. 1. The thin-filmforming apparatus may include a reaction tube 103 including afilm-forming chamber (a processing chamber 101) configured to processsubstrates 100, a boat 102 configured to hold the substrate 100 in thefilm-forming chamber 101 in multiple stages in a horizontal posture, aheating source 104 disposed around the reaction tube 103, a processinggas supply line 105 through which a processing gas for forming the CVDthin film is supplied into the film-forming chamber 101, a cleaning gassupply line 107 a through which an NF₃ gas serving as a cleaning gas forremoving a deposit via an etching process is supplied into thefilm-forming chamber 101, an additional gas supply line 107 b throughwhich an NO gas to be added to the cleaning gas is supplied, and anexhaust line 108 at which a pressure adjustment valve 106 for adjustingan inner pressure of the film-forming chamber 101 and a vacuum pump 109are installed sequentially from an upstream side. The reaction tube 103and the boat 102 are made of quartz (SiO₂).

Hereinafter, the thin-film forming process using the above-describedthin-film forming apparatus will be described. First, the boat 102holding the substrates 100 is loaded into the film-forming chamber 101.Thereafter, a surface of each of the substrates 100 is heated by theheating source 104 to a predetermined temperature. Afterwards, theprocessing gas is supplied through the processing gas supply line 105into the film-forming chamber 101 while exhausting an inside of thefilm-forming chamber 101 through the exhaust line 108, and a thin filmis then formed on the substrates 100 by a CVD reaction. A pressure ofthe film-forming chamber 101 is adjusted by the pressure adjustmentvalve 106 installed at the exhaust line 108 in order to maintain thepressure of the film-forming chamber 101 at a predetermined pressure.When the thin film having a predetermined thickness is formed on thesubstrates 100, the supply of the processing gas from the processing gassupply line 105 is stopped. Thereafter, the substrates 100 having thethin film formed thereon are cooled to a predetermined temperature, andthe boat 102 is then unloaded from the film-forming chamber 101.

The above-described thin-film forming process is originally for formingthe thin film on the substrate 100. However, when the thin film isformed on the substrate 100, a deposit including the thin film isactually adhered to surfaces of members such as an inner wall of thereaction tube 103 that constitutes the film-forming chamber 101 and theboat 102 each time the above-described thin-film forming process isperformed. When the deposit reaches a predetermined thickness or more,the deposit is delaminated or dropped, thereby generating foreignmatters on the substrate 100. Therefore, the deposit should be removedwhenever the deposit reached the predetermined thickness.

Conventionally, a wet cleaning process including separating the reactiontube 103 from the substrate processing apparatus, dipping the reactiontube 103 in a cleaning solution including an HF solution, and removingthe deposit by wet etching has been mainly adopted as a method forremoving the deposit.

In recent years, however, a dry cleaning process wherein the reactiontube is not separated is increasingly used. The dry cleaning processincludes directly supplying a gas (hereinafter, referred to as a“cleaning gas”) containing fluorine (F) atoms and a dilution gas into aprocessing chamber and removing a silicon-based deposit such as a Si₃N₄film by etching by controlling a temperature, a pressure, and a gas flowrate in the processing chamber. In addition, a technique of adding a gascontaining oxygen (O) atoms to the cleaning gas is known as a means forimproving the performance (i.e., etching rate) of the cleaning process(for example, refer to Japanese Patent Laid-Open Publication Nos. HEI10-303186 and 2005-101583).

Furthermore, a technique using a FNO gas as the cleaning gas is alsoknown (for example, Japanese Patent Laid-Open Publication No.2003-144905.

A nitrogen monoxide (NO) gas is popular as the gas containing oxygenatoms to be added to the cleaning gas. However, when the NO gas is addedto the cleaning gas, processing conditions such as a temperature and apressure need to be adjusted to a high temperature and a high pressureor a cleaning rate is reduced. For example, when a nitrogen trifluoride(NF₃) gas is used as the cleaning gas, the processing chamber must bemaintained under the condition of the high temperature and the highpressure in order to cause a sufficient reaction of the NF₃ gas with theNO gas due to a low reactivity of the NF₃ gas with the NO gas. Moreover,when a fluorine (F₂) gas is used as the cleaning gas, the F₂ gasexcessively reacts with the NO gas due to a high reactivity of the F₂gas with the NO gas, resulting in a degradation of the cleaning rate.That is, the addition of the NO gas to the cleaning gas results in adifficulty in handling and a degradation of a controllability of thecleaning performance.

In addition, when the FNO gas is used as the cleaning gas, the cleaningprocess is not performed in some cases. While the FNO gas added to thecleaning gas accelerates an etching reaction by the cleaning gas, usingonly the FNO gas does not facilitate an etching process due to a lowetching rate. Furthermore, FNO is not commercialized as a gas presently,and an immediate adoption of the FNO gas as the cleaning gas isdifficult. Furthermore, the above-described problems have been onlydiscovered in latest research conducted by the inventors.

Hereinafter, the dry cleaning method will be briefly described. First,the empty boat 102 having the deposit adhered thereon is loaded into thereaction tube 103, namely, into the film-forming chamber 101 also havingthe deposit adhered thereon. Thereafter, the inside of the film-formingchamber 101 is heated by the heating source 104 to a predeterminedtemperature. Next, the NF₃ gas is supplied through the cleaning gassupply line 107 a into the film-forming chamber 101 while exhausting theinside of the film-forming chamber 101 through the exhaust line 108, andthe deposit adhered to the inside of the film-forming chamber 101,namely, the inner wall of the reaction tube 103 or the surface of theboat 102, is removed due to an etching reaction of active speciesgenerated by a decomposition of the cleaning gas with the deposit. Here,the NO gas is supplied from the additional gas supply line 107 b and isadded to the NF₃ gas supplied into the film-forming chamber 101 toimprove the etching rate. Further, the pressure in the film-formingchamber 101 is adjusted by the pressure adjustment valve 106 installedat the exhaust line 108 in order to maintain the pressure of thefilm-forming chamber 101 at the predetermined pressure. When the depositis removed from the film-forming chamber 101, the supply of the cleaninggas from the cleaning gas supply line 107 is stopped. Thereafter, aseasoning process is performed in the film-forming chamber 101. That is,the processing gas is supplied into the film-forming chamber 101 withthe substrate 100 unloaded therefrom, and the thin film is formed(pre-coated) on the inner wall of the reaction tube 103 or the surfaceof the boat 102 in the film-forming chamber 101 so that the film-formingchamber 101 can be restored to a state in which the film forming processmay be performed.

In addition to the NF₃ gas as the nitrogen fluoride gas, a F₂ gas may beused as the cleaning gas. However, as described above, when the NF₃ gasis used as the cleaning gas, the processing chamber must be maintainedunder the condition of the high temperature, for example 600° C. and thehigh pressure in order to cause the sufficient reaction of the NF₃ gaswith the NO gas due to the low reactivity of the NF₃ gas with the NOgas. Moreover, when the F₂ gas is used as the cleaning gas, the F₂ gasexcessively reacts with the NO gas due to a high reactivity of the F₂gas with the NO gas, resulting in a degradation of the cleaning rate.That is, the addition of the NO gas to the cleaning gas results in thedifficulty in handling and the degradation of the controllability of thecleaning performance.

In addition, a technique wherein only the FNO gas is used as thecleaning gas is also known. However, when only the FNO gas is used asthe cleaning gas, the cleaning process is not performed in some casesaccording to the research by the inventors. While the FNO gas added tothe cleaning gas accelerates the etching reaction by the cleaning gas,using only the FNO gas does not facilitate the etching process due tothe low etching rate. Furthermore, FNO is not commercialized as the gaspresently, and the immediate adoption of the FNO gas as the cleaning gasis difficult.

SUMMARY

It is an object of the present invention to provide a substrateprocessing apparatus, a method of manufacturing a semiconductor deviceand a method of cleaning a processing vessel which facilitates thehandling of the cleaning gas and improve the controllability of thecleaning performance when the dry cleaning process is performed in theprocessing chamber by adding the NO gas to the cleaning gas.

According to one embodiment of the present invention, there is provideda substrate processing apparatus including: a processing vesselconfigured to process a substrate; a processing gas supply systemconfigured to supply a processing gas into the processing vessel; afirst cleaning gas supply system configured to supply a pre-mixed gasincluding a fluorine-containing gas and a nitrogen monoxide gas into theprocessing vessel; a second cleaning gas supply system installed apartfrom the first cleaning gas supply system and configured to supply thefluorine-containing gas into the processing vessel; and a controllerconfigured to control the processing gas supply system, the firstcleaning gas supply system, and the second cleaning gas supply system ina manner that the processing gas is supplied into the processing vesselaccommodating the substrate to form a thin film on the substrate, andthat the pre-mixed gas and the fluorine-containing gas is supplied intothe processing vessel through the first cleaning gas supply system andthe second cleaning gas supply system respectively so as to remove adeposit containing the thin film adhered to an inside of the processingvessel.

According to another embodiment of the present invention, there isprovided a substrate processing apparatus including: a processing vesselconfigured to process a substrate; a processing gas supply systemconfigured to supply a processing gas into the processing vessel; afirst cleaning gas supply system comprising a preliminary decompositionchamber for decomposing a fluorine-containing gas, the first cleaninggas supply system configured to supply a pre-mixed gas including a gasobtained from decomposing the fluorine-containing gas in the preliminarydecomposition chamber and a nitrogen monoxide gas into the processingvessel;

a second cleaning gas supply system installed apart from the firstcleaning gas supply system and configured to supply thefluorine-containing gas into the processing vessel; and a controllerconfigured to control the processing gas supply system, the firstcleaning gas supply system, and the second cleaning gas supply system ina manner that the processing gas is supplied into the processing vesselaccommodating the substrate to form a thin film on the substrate, andthat the pre-mixed gas and the fluorine-containing gas is supplied intothe processing vessel through the first cleaning gas supply system andthe second cleaning gas supply system respectively so as to remove adeposit containing the thin film adhered to an inside of the processingvessel.

According to still another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, including:supplying a processing gas into a processing vessel accommodating asubstrate to form a thin film on the substrate; and supplying apre-mixed gas including a fluorine-containing gas and a nitrogenmonoxide gas into the processing vessel through a first cleaning gassupply system while simultaneously supplying the fluorine-containing gasinto the processing vessel through a second cleaning gas supply systeminstalled apart from the first cleaning gas supply system so as toremove a deposit containing the thin film adhered to an inside of theprocessing vessel.

According to yet another embodiment of the present invention, there isprovided a method of manufacturing a semiconductor device, including:supplying a processing gas into a processing vessel accommodating asubstrate to form a thin film on the substrate; and supplying apre-mixed gas including a gas obtained from decomposing afluorine-containing gas in a preliminary decomposition chamber and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto an inside of the processing vessel.

According to yet another embodiment of the present invention, there isprovided a method of cleaning an inside of a processing vesselincluding: providing the processing vessel configured to process asubstrate to form a thin film thereon; and supplying a pre-mixed gasincluding a fluorine-containing gas and a nitrogen monoxide gas into theprocessing vessel through a first cleaning gas supply system whilesimultaneously supplying the fluorine-containing gas into the processingvessel through a second cleaning gas supply system installed apart fromthe first cleaning gas supply system so as to remove a depositcontaining the thin film adhered to the inside of the processing vessel.

According to yet another embodiment of the present invention, there isprovided a method of cleaning an inside of a processing vesselincluding: providing the processing vessel configured to process asubstrate to form a thin film thereon; and supplying a pre-mixed gasincluding a gas obtained from decomposing a fluorine-containing gas in apreliminary decomposition chamber and a nitrogen monoxide gas into theprocessing vessel through a first cleaning gas supply system whilesimultaneously supplying the fluorine-containing gas into the processingvessel through a second cleaning gas supply system installed apart fromthe first cleaning gas supply system so as to remove a depositcontaining the thin film adhered to the inside of the processing vessel.

According to a substrate processing apparatus, a method of manufacturinga semiconductor device and a method of cleaning a processing vessel ofthe present invention, when the dry cleaning process is performed in theprocessing chamber by adding the nitrogen monoxide (NO) gas to thecleaning gas, the handling is facilitated, and the controllability ofthe cleaning performance is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram schematically illustrating a typicalchemical-vapor-deposition (CVD) thin-film forming apparatus for asemiconductor.

FIG. 2 is a configuration diagram schematically illustrating aprocessing furnace of a substrate processing apparatus according to oneembodiment of the present invention.

FIG. 3 is a configuration diagram schematically illustrating aprocessing furnace of a substrate processing apparatus according toanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As described above, a CVD thin film is formed by supplying a processinggas into a processing chamber having a substrate loaded therein.Hereinafter, a configuration of a typical thin-film forming apparatusand a typical thin-film forming process will be briefly described.

Therefore, the inventors have conducted assiduous research on a methodfor performing a dry cleaning process in a processing chamber whichfacilitates the handling of the cleaning gas and improve thecontrollability of the cleaning performance As a result, the inventorscame to a conclusion that the above-described problems can be solved byadding the FNO to a gas containing F atoms. That is, the inventors areof an opinion that the above-described problems can be solved by causinga state where the fluorine-containing gas and the FNO gas exist togethersince the FNO gas serves to accelerate an etching reaction by thefluorine-containing gas. The present invention is based on theinventors' findings.

Hereinafter, one embodiment of the present invention will be described.

(1) Configuration of Substrate Processing Apparatus

First, the configuration of the substrate processing apparatus accordingto the embodiment of the present invention will be described withreference to the accompanying drawings. FIG. 2 is a configurationdiagram schematically illustrating a processing furnace 202 of thesubstrate processing apparatus according to one embodiment, which isdepicted in a longitudinal sectional view.

As shown in FIG. 2, the processing furnace 202 may include a heater 206serving as a heating mechanism. The heater 206 has a cylindrical shapeand is supported by a heater base 251 serving as a holding plate andvertically installed.

A process tube 203 serving as a reaction tube is installed inside theheater 206. The process tube 203 is concentric with the heater 206. Theprocess tube 203 includes an inner tube 204 serving as an internalreaction tube and an outer tube 205 serving as an external reaction tubeinstalled outside the inner tube 204. The inner tube 204 is made of aheat-resistant material, such as quartz (SiO₂) or silicon carbide (SiC),and has a cylindrical shape with open upper and lower ends. A processingchamber 201 wherein a process of forming a thin film on a wafer 200serving as a substrate is performed is formed in a cylindrical hollowportion of the inner tube 204. The processing chamber 201 is capable ofaccommodating the wafers 200 in a horizontal posture aligned in multiplestages in a vertical direction by means of a boat 217 which is describedlater. The outer tube 205 is made of the heat-resistant material, forexample, quartz or silicon carbide and has an inner diameter greaterthan an outer diameter of the inner tube 204. The outer tube 205 has acylindrical shape with a closed upper end and an open lower end and isconcentric with the inner tube 204.

A manifold 209 concentric with the outer tube 205 is installed below theouter tube 205. The manifold 209 is made of, for example, a stainlesssteel or the like and has a cylindrical shape with open upper and lowerends. The manifold 209 is engaged with the inner tube 204 and the outertube 205 and installed to support the inner tube 204 and the outer tube205. Also, an O-ring 220 a serving as a sealing member is installedbetween the manifold 209 and the outer tube 205. By supporting themanifold 209 by the heater base 251, the process tube 203 is verticallyinstalled. The process tube 203 and the manifold 209 constitute areaction vessel serving as a processing vessel.

Nozzles 230 a and 230 b serving as gas introduction members areconnected to the manifold 209 such that the nozzles 230 a and 230 bcommunicate with the inside of the processing chamber 201. Processinggas supply pipes 232 a and 232 b through which a processing gas forforming a thin film is supplied into the processing chamber 201 areconnected to the nozzles 230 a and 230 b, respectively. A SiH₂Cl₂(dichlorosilane or DCS) gas supply source 271 serving as a firstprocessing gas supply source is connected to an upstream side of theprocessing gas supply pipe 232 a, which is disposed opposite to aconnection portion between the processing gas supply pipe 232 a and thenozzle 230 a, via a mass-flow controller (MFC) 241 a serving as a gasflow rate controller. Valves 262 a and 261 a are respectively installedat upstream and downstream sides of the MFC 241 a in the processing gassupply pipe 232 a. An NH₃ gas supply source 272 serving as a secondprocessing gas supply source is connected to an upstream side of theprocessing gas supply pipe 232 b, which is disposed opposite to aconnection portion between the processing gas supply pipe 232 b and thenozzle 230 b, via an MFC 241 b serving as the gas flow rate controller.Valves 262 b and 261 b are installed at upstream and downstream sides ofthe MFC 241 b in the processing gas supply pipe 232 b. Mainly, theprocessing gas supply system is constituted by the processing gas supplypipes 232 a and 232 b, the MFCs 241 a and 241 b, the valves 262 a, 261a, 262 b, and 261 b, the SiH₂Cl₂ gas supply source 271, and the NH₃ gassupply source 272.

Inert gas supply pipes 232 c and 232 d are respectively connected todownstream sides of the valves 261 a and 261 b in the processing gassupply pipes 232 a and 232 b. An N₂ gas supply source 273 serving as aninert gas supply source is connected to an upstream side of the inertgas supply pipe 232 c, which is disposed opposite to a connectionportion between the inert gas supply pipe 232 c and the processing gassupply pipe 232 a, via an MFC 241 c serving as the gas flow ratecontroller. Valves 262 c and 261 c are respectively installed atupstream and downstream sides of the MFC 241 c in the inert gas supplypipe 232 c. The N₂ gas supply source 273 is connected to an upstreamside of the inert gas supply pipe 232 d, which is disposed opposite to aconnection portion between the inert gas supply pipe 232 d and theprocessing gas supply pipe 232 b, via an MFC 241 d serving as the gasflow rate controller. Specifically, the upstream side of the inert gassupply pipe 232 d is connected to an upstream side of the valve 262 c inthe inert gas supply pipe 232 d, while the upstream side of the valve262 c of the inert gas supply pipe 232 d is branched from the inert gassupply pipe 232 c. Valves 262 d and 261 d are respectively installed atupstream and downstream sides of the MFC 241 d in the inert gas supplypipes 232 d. Mainly, the inert gas supply system is constituted by theinert gas supply pipes 232 c and 232 d, the MFCs 241 c and 241 d, thevalves 262 c, 261 c, 262 d, and 261 d, and the N₂ gas supply source 273.Also, the inert gas supply system functions to dilute the processing gasor the cleaning gas and constitutes a portion of the processing gassupply system or a cleaning gas supply system. In addition, the inertgas supply system also functions as a purge gas supply system.

A downstream end of a first cleaning gas supply pipe 232 h through whicha pre-mixed gas including a gas obtained from decomposing a gascontaining fluorine atoms and a nitrogen monoxide (NO) gas is suppliedinto the processing chamber 201 is connected to a downstream side of aconnection portion between the processing gas supply pipe 232 b and theinert gas supply pipe 232 d as the downstream side of the valve 261 b inthe processing gas supply pipe 232 b. Each of a downstream end of an theNF₃ gas supply pipe 232 f through which the NF₃ gas is supplied and adownstream end of an the NO gas supply pipe 232 g through which the NOgas is supplied is connected to an upstream side of the first cleaninggas supply pipe 232 h, which is disposed opposite to a connectionportion between the first cleaning gas supply pipe 232 h and theprocessing gas supply pipe 232 b. The NF₃ gas supply source 274, a valve262 f, an MFC 241 f serving as the gas flow rate controller, a valve 261f, and a preliminary decomposition chamber 280 f configured to decomposethe NF₃ gas are installed sequentially from an upstream side of the NF₃gas supply pipe 232 f. The NO gas supply source 275, a valve 262 g, anMFC 241 g serving as the gas flow rate controller and a valve 261 g areinstalled sequentially from an upstream side of the NO gas supply pipe232 g. The preliminary decomposition chamber 280 f decomposes the NF₃gas serving as the gas containing F atoms using plasma or heat andgenerates the F₂ gas. For example, a plasma source or a heater may beemployed as a decomposition source for decomposing the NF₃ gas. Mainly,the first cleaning gas supply system is constituted by the firstcleaning gas supply pipe 232 h, the NF₃ gas supply pipe 232 f, the NOgas supply pipe 232 g, the MFCs 241 f and 241 g, the valves 262 f, 261f, 262 g, and 261 g, the preliminary decomposition chamber 280 f, theNF₃ gas supply source 274, and the NO gas supply source 275.

By opening the valves 262 f and 261 f, the NF₃ gas supplied from the NF₃gas supply source 274 is adjusted in terms of flow rate by the MFC 241f, supplied into the preliminary decomposition chamber 280 f, anddecomposed into the F₂ gas and an N₂ gas. The F₂ gas generated in thepreliminary decomposition chamber 280 f is supplied into the firstcleaning gas supply pipe 232 h via the NF₃ gas supply pipe 232 f. Byfurther opening the valves 262 g and 261 g, the NO gas supplied from thegas supply source 275 is adjusted in terms of flow rate by the MFC 241 gand supplied into the first cleaning gas supply pipe 232 h via the NOgas supply pipe 232 g. Thereafter, the F₂ gas is mixed with the NO gasin the first cleaning gas supply pipe 232 h to generate the FNO. A gascontaining the generated FNO is supplied into the processing chamber 201via the first cleaning gas supply pipe 232 h, the processing gas supplypipe 232 b, and the nozzle 230 b. Accordingly, in accordance with thepresent embodiment, the F₂ gas generated by the preliminarydecomposition and the NO gas are mixed in advance (pre-mixed) with eachother in the first cleaning gas supply pipe 232 h before being suppliedinto the processing chamber 201 instead of separately supplying each ofthe F₂ gas and the NO gas into the processing chamber 201. Thus, thegeneration efficiency of the FNO can be improved. On the other hand,when the F₂ gas and the NO gas are separately supplied into theprocessing chamber 201, a reaction of the F₂ gas with the NO gasinsufficiently occurs, thereby reducing the generation efficiency of theFNO.

In addition, by elongating a flow path [the first cleaning gas supplypipe 232 h and a downstream side of a connection portion between thefirst cleaning gas supply pipe 232 h and the processing gas supply pipe232 b through which the F₂ gas generated by the preliminarydecomposition and the NO gas meet each other and flow into theprocessing chamber 201, reactivity between the F₂ gas and the NO gas canbe further increased, and the generation efficiency of the FNO can befurther improved. In other words, when a mixture of the F₂ gas generatedby the preliminary decomposition and the NO gas is supplied into theprocessing chamber 201 in an extremely short time after the F₂ gas ismixed with the NO gas, a reaction of the F₂ gas with the NO gasinsufficiently occurs in some cases. However, by adjusting the flow pathdescribed above, the F₂ gas may sufficiently react with the NO gas.

A downstream end of a second cleaning gas supply pipe 232 e throughwhich the NF₃ gas serving as the gas containing F atoms is supplied intothe processing chamber 201 is connected to a downstream side of aconnection portion between the processing gas supply pipe 232 a and theinert gas supply pipe 232 c as the downstream side of the valve 261 a inthe processing gas supply pipe 232 a. An upstream end of the secondcleaning gas supply pipe 232 e is connected to an upstream side of thevalve 262 f in the NF₃ gas supply pipe 232 f. A valve 262 e, an MFC 241e serving as the gas flow rate controller, and a valve 261 e areinstalled sequentially from the upstream side of the second cleaning gassupply pipe 232 e. Mainly, a second cleaning gas supply system isconstituted by the NF₃ gas supply pipe 232 f, the second cleaning gassupply pipe 232 e, the MFC 241 e, the valves 262 e and 261 e, and theNF₃ gas supply source 274.

By opening the valves 262 e and 261 e, the NF₃ gas supplied from the NF₃gas supply source 274 is adjusted in terms of flow rate by the MFC 241 eand supplied into the processing chamber 201 via the second cleaning gassupply pipe 232 e, the processing gas supply pipe 232 a, and the nozzle230 a. Thus, in accordance with the embodiment, the second cleaning gassupply system is installed apart from the first cleaning gas supplysystem. Also, the gas containing the FNO supplied from the firstcleaning gas supply system and the fluorine-containing gas supplied fromthe second cleaning gas supply system are separately supplied into theprocessing chamber 201 and mixed for the first time (post-mixed) in theprocessing chamber 201.

A gas supply/flow rate controller 235 is electrically connected to theMFCs 241 a, 241 b, 241 c, 241 d, 241 e, 241 f, and 241 g, the valves 261a, 261 b, 261 c, 261 d, 261 e, 261 f, 261 g, 262 a, 262 b, 262 c, 262 d,262 e, 262 f, and 262 g and the preliminary decomposition chamber 280 f.The gas supply/flow rate controller 235 is configured to control theMFCs 241 a, 241 b, 241 c, 241 d, 241 e, 241 f, and 241 g and the valves261 a, 261 b, 261 c, 261 d, 261 e, 261 f, 261 g, 262 a, 262 b, 262 c,262 d, 262 e, 262 f, and 262 g at desired time points such that desiredtypes of gases are supplied at desired flow rates and desiredconcentrations into the processing chamber 201 in each of stepsdescribed later. In addition, the gas supply/flow rate controller 235 isconfigured to control operations of the decomposition source of thepreliminary decomposition chamber 280 f such as the plasma source or theheater.

An exhaust pipe 231 configured to exhaust an atmosphere from theprocessing chamber 201 is installed at the manifold 209. The exhaustpipe 231 is disposed at a lower end portion of a cylindrical space 250defined by a gap between the inner tube 204 and the outer tube 205 andcommunicates with the cylindrical space 250. A vacuum exhaust device246, such as a vacuum pump, is connected to a downstream side of theexhaust pipe 231, which is disposed opposite to a connection portionbetween the exhaust pipe 231 and the manifold 209, via a pressure sensor245 serving as a pressure detector and a variable conductance valve, forexample, a pressure adjustment device 242 such as an auto-pressurecontroller (APC) valve. The vacuum exhaust device 246 is configured tovacuum-exhaust the inside of the processing chamber 201 such that apressure in the processing chamber 201 reaches a predetermined pressure(degree of vacuum). A pressure controller 236 is electrically connectedto the pressure adjustment device 242 and the pressure sensor 245. Thepressure controller 236 is controls the pressure adjustment device 242at a desired time point based on a pressure detected by the pressuresensor 245 so that the pressure in the processing chamber 201 maintainsa desired pressure. Mainly, the exhaust system is constituted by theexhaust pipe 231, the pressure adjustment device 242, and the vacuumdevice 246.

A seal cap 219 is installed under the manifold 209 and serves as a firstfurnace-opening cover body capable of closing a lower end opening of themanifold 209 in an air tight manner. The seal cap 219 is configured toabut with a lower end of the manifold 209 upward in a verticaldirection. The seal cap 219 is made of a metal, such as stainless steel,and has a disk shape. An O-ring 220 b serving as the sealing memberabutting with the lower end of the manifold 209 is installed on a topsurface of the seal cap 219. A rotation mechanism 254 configured torotate the boat is installed at a side of the seal cap 219 opposite tothe processing chamber 201. A rotation axis 255 of the rotationmechanism 254 is connected to the boat 217 to be described later throughthe seal cap 219 and configured to rotate the wafer 200 by rotating theboat 217. The seal cap 219 is configured to move up and down in avertical direction by means of a boat elevator 115 serving as anelevating mechanism installed vertically outside the process tube 203such that the boat 217 may be loaded into or unloaded from theprocessing chamber 201. A driving controller 237 is electricallyconnected to the rotation mechanism 254 and the boat elevator 115. Thedriving controller 237 is configured to control the rotation mechanism254 and the boat elevator 115 at desired time points such that therotation mechanism 254 and the boat elevator 115 perform desiredoperations. In addition, a shutter 219 a is installed under the manifold209 and serves as a second furnace-opening cover body capable of closingthe lower end opening of the manifold 209 in the air tight manner. Theshutter 219 a is configured to be lifted/lowered and rotated. Theshutter 219 a is configured to abut with the lower end of the manifold209 after the boat 217 is unloaded from the processing chamber 201, andto close the inside of the processing chamber 201 having the boat 217unloaded in the air tight manner. An O-ring 220 c serving as the sealingmember abutting with the lower end of the manifold 209 is installed on atop surface of the shutter 219 a.

The boat 217 serving as a substrate holder is made of the heat-resistantmaterial, such as quartz or silicon carbide, and is configured to aligncenters of a plurality of wafers 200 with one another and hold theplurality of wafers 200 in multiple stages in a horizontal posture.Further, a plurality of insulation plates 216 serving as disk-shapedinsulation members are made of the heat-resistant material, such asquartz or silicon carbide, disposed in a lower portion of the boat 217in multiple stages in a horizontal posture and configured to precludetransmission of heat from the heater 206 from reaching the side of themanifold 209.

A temperature sensor 263 serving as a temperature detector is installedin the process tube 203. A temperature controller 238 is electricallyconnected to the heater 206 and the temperature sensor 263. Thetemperature controller 238 controls a conduction state to the heater 206at desired time points based on temperature information detected by thetemperature sensor 263 such that the inside of the processing chamber201 has a desired temperature distribution.

The gas supply/flow rate controller 235, the pressure controller 236,the driving controller 237, and the temperature controller 238 alsoconstitute a manipulation unit and an input/output (I/O) unit and areelectrically connected to a main controller 239 configured to controlthe entire substrate processing apparatus. The gas supply/flow ratecontroller 235, the pressure controller 236, the driving controller 237,the temperature controller 238, and the main controller 239 constitute acontroller 240.

(2) Thin-Film Forming Process

Hereinafter, as one process of a processes for manufacturing asemiconductor device, a process of forming a thin film on the wafer 200in the processing chamber 201 using a CVD technique by means of theprocessing furnace 202 having the above-described configuration will bedescribed. Further, in the following description, the operation of eachcomponent constituting the substrate processing apparatus is controlledby the controller 240.

When the plurality of wafers 200 are charged in the boat 217 (wafercharging), as shown in FIG. 2, the boat 217 holding the plurality ofwafers 200 is lifted by the boat elevator 115 and loaded into theprocessing chamber 201 (boat loading). The lower end of the manifold 209is sealed by the seal cap 219 via the O-ring 220 b.

The processing chamber 201 is vacuum-exhausted by the vacuum exhaustdevice 246 such that the inner pressure thereof is lowered to a desiredpressure (degree of vacuum). Here, the inner pressure of the processingchamber 201 is measured by the pressure sensor 245, and the pressureadjustment device 242 is feedback-controlled based on the measuredpressure information. In addition, the processing chamber 201 is heatedby the heater 206, such that the temperature therein reaches a desiredtemperature. Here, a conduction state to the heater 206 isfeedback-controlled based on temperature information detected by thetemperature sensor 263 such that the inside of the processing chamber201 has the desired temperature distribution. Subsequently, the boat 217is rotated by the rotation mechanism 254, thereby rotating the wafer200.

Next, SiH₂Cl₂ gas serving as a first processing gas and NH₃ gas servingas a second processing gas are respectively supplied from the SiH₂Cl₂gas supply source 271 serving as the first processing gas supply sourceand the NH₃ gas supply source 272 serving as the second processing gassupply source into the processing chamber 201 with the inside of theprocessing chamber 201 being at the desired temperature under thedesired pressure. That is, by opening the valves 262 a, 261 a, 262 b,and 261 b, the SiH₂Cl₂ gas and the NH₃ gas supplied from the SiH₂Cl₂ gassupply source 271 and the NH₃ gas supply source 272 into the processinggas supply pipes 232 a and 232 b, respectively, are controlled to havedesired flow rates by the MFCs 241 a and 241 b, respectively, and areintroduced from the nozzles 230 a and 230 b through the processing gassupply pipes 232 a and 232 b, respectively, into the processing chamber201.

Simultaneously, the N₂ gas may be supplied from the N₂ gas supply source273 serving as the inert gas supply source into the processing chamber201 and the processing gases (the SiH₂Cl₂ gas and the NH₃ gas) may bediluted with the N₂ gas. In this case, for example, by opening thevalves 262 c, 261 c, 262 d, and 261 d, the N₂ gas supplied from the N₂gas supply source 273 into each of the inert gas supply pipes 232 c and232 d is controlled to have a desired flow rate by each of the MFCs 241c and 241 d, passes through each of the inert gas supply pipes 232 c and232 d, and is introduced from each of the nozzles 230 a and 230 b viaeach of the processing gas supply pipes 232 a and 232 b into theprocessing chamber 201. The N₂ gas is mixed with the SiH₂Cl₂ gas and theNH₃ gas in the processing gas supply pipes 232 a and 232 b,respectively. The concentration of the processing gas may be controlledby controlling the flow rate of the supplied N₂ gas.

The processing gas introduced into the processing chamber 201 goes upinside the processing chamber 201, flows out from an upper end openingof the inner tube 204 into the cylindrical space 250, flows down in thecylindrical space 250, and is exhausted through the exhaust pipe 231.While passing through the processing chamber 201, the processing gascontacts the surface of the wafer 200. The thin film, that is, a siliconnitride (Si₃N₄) film, is deposited on the surface of the wafer 200 by athermal CVD reaction.

After a predetermined processing time has elapsed, the supply of theprocessing gas is stopped. That is, by closing the valves 262 a, 261 a,262 b, and 261 b, the supply of the SiH₂Cl₂ gas and the NH₃ gas from theSiH₂Cl₂ gas supply source 271 and the NH₃ gas supply source 272 into theprocessing chamber 201 is stopped. Thereafter, by opening the valves 262c, 261 c, 262 d, and 261 d, the N₂ gas is supplied from the N₂ gassupply source 273 into the processing chamber 201 and is exhaustedthrough the exhaust pipe 231 to purge the inside of the processingchamber 201. in addition, an inner atmosphere of the processing chamber201 is replaced by the N₂ gas so that an inner pressure of theprocessing chamber 201 returns to atmospheric pressure.

Thereafter, the seal cap 219 is lowered by the boat elevator 115 to opena lower end of the manifold 209 and simultaneously, the processed wafer200 is unloaded (boat unloading) from the lower end of the manifold 209out of the process tube 203 with the processed wafer 200 held by theboat 217. Afterwards, the processed wafer 200 is discharged from theboat 217 (wafer discharging).

Meanwhile, processing conditions when processing the wafers 200 in theprocessing furnace 202 of the present embodiment, for example, information of the silicon nitride film, are as follows:

Processing temperature: 650 to 800° C.,

Processing pressure: 10 to 500 Pa,

Supply flow rate of the SiH₂Cl₂ gas: 100 to 500 sccm,

Supply flow rate of the NH₃ gas: 500 to 5,000 sccm.

The processing of the wafer 200 is performed by maintaining therespective processing conditions constant within the respective ranges.

(3) Cleaning Process

Hereinafter, a method for cleaning the inside of the processing chamber201 will be described. In addition, in the following description,operations of respective components of the substrate processingapparatus are controlled by the controller 240.

By repeating the above-described thin-film forming process, the thinfilm, such as the silicon nitride film, is accumulated inside theprocessing chamber including the inner wall of the process tube 203.That is, the deposit including the thin film is adhered to the innerwall of the process tube 203. The cleaning process is performed in theprocessing chamber 201 at a time point when the deposit (accumulatedthin film) adhered to the inner wall of the process tube 203 reaches thepredetermined thickness before the deposit delaminates or drops. Thecleaning process includes supplying, from the first cleaning gas supplysystem into the processing chamber 201 a, a pre-mixed gas obtained bypre-mixing a gas obtained from decomposing the NF₃ gas in thepreliminary decomposition chamber 280 f with the NO gas, and exhaustingthe pre-mixed gas from the processing chamber 201, while simultaneouslysupplying the NF₃ gas from the second cleaning gas system installedapart from the first cleaning gas supply system and exhausting the NF₃gas, with the processed wafer 200 discharged from the processing chamber201, to remove the deposit adhered to the processing chamber 201.

Hereinafter, the cleaning process will be described in detail.

The empty boat 217 in which the wafer 200 is not charged is lifted bythe boat elevator 115 and loaded (boat loading) into the processingchamber 201. The seal cap 219 is in a state of sealing a lower end ofthe manifold 209 via the O-ring 220 b.

The processing chamber 201 is vacuum-exhausted by the vacuum exhaustdevice 246 such that the inner pressure thereof is lowered to a desiredpressure (degree of vacuum). Here, the inner pressure of the processingchamber 201 is measured by the pressure sensor 245, and the pressureadjustment device 242 is feedback-controlled based on the measuredpressure information. In addition, the processing chamber 201 is heatedby the heater 206, such that the temperature therein reaches a desiredtemperature. Here, a conduction state to the heater 206 isfeedback-controlled based on temperature information detected by thetemperature sensor 263 such that the inside of the processing chamber201 has the desired temperature distribution. When the inner pressureand the temperature of the processing chamber 201 reach thepredetermined pressure and the predetermined temperature, respectively,control is performed to maintain the predetermined pressure and thepredetermined temperature. Subsequently, the boat 217 is rotated by therotation mechanism 254. However, the boat 217 may not be rotated.

Thereafter, while maintaining the inner temperature and pressure of theprocessing chamber 201 at the predetermined temperature and thepredetermined pressure, the pre-mixed gas including the gas obtained bydecomposing the NF₃ gas in the preliminary decomposition chamber 280 fand the NO gas is supplied into the processing chamber 201 from thefirst cleaning gas supply system, and the pre-mixed gas is exhaustedfrom the processing chamber 201, and the NF₃ gas is simultaneouslysupplied from the second cleaning gas supply system installed apart fromthe first cleaning gas supply system and the NF₃ is exhausted to cleanthe processing chamber 201.

Specifically, by opening the valves 262 f and 261 f, the NF₃ gassupplied from the NF₃ gas supply source 274 is adjusted in terms of flowrate by the MFC 241 f. The NF₃ gas is then supplied into the preliminarydecomposition chamber 280 f via the NF₃ gas supply pipe 232 f anddecomposed into F₂ gas and N₂ gas, and supplied into the first cleaninggas supply pipe 232 h. In this case, by further opening the valves 262 gand 261 g, the NO gas supplied from the NO gas supply source 275 isadjusted in terms of flow rate by the MFC 241 g and supplied into thefirst cleaning gas supply pipe 232 h via the NO gas supply pipe 232 g.Thereafter, FNO is generated by pre-mixing the F₂ gas with the NO gas inthe first cleaning gas supply pipe 232 h, and a gas containing the FNOis supplied into the processing chamber 201 via the first cleaning gassupply pipe 232 h, the processing gas supply pipe 232 b, and the nozzle230 b. The F₂ gas generated by the preliminary decomposition and the NOgas are mixed in advance (pre-mixed) with each other in the firstcleaning gas supply pipe 232 h before being supplied into the processingchamber 201 instead of separately supplying each of the F₂ gas and theNO gas into the processing chamber 201, thereby improving a generationefficiency of the FNO.

By opening the valves 262 e and 261 e simultaneously with the initiationof the supply of the gas containing the FNO into the processing chamber201, the NF₃ gas supplied from the NF₃ gas supply source 274 is adjustedin terms of flow rate by the MFC 241 e and supplied into the processingchamber 201 via the second cleaning gas supply pipe 232 e, theprocessing gas supply pipe 232 a, and the nozzle 230 a.

In addition, when a rate of the decomposition of the NF₃ gas in thepreliminary decomposition chamber 280 f is 100%, the NF₃ gas isdecomposed according to a reaction formula 2NF₃→3F₂+N₂. Assuming thatthe NF₃ gas is supplied at a flow rate of 1 slm into the preliminarydecomposition chamber 280 f, a decomposed gas (a mixture gas of the F₂gas and the N₂ gas) containing 75% of F₂ and 25% of N₂ is supplied at aflow rate of 2 slm into the first cleaning gas supply pipe 232 h. Inthis case, assuming that the NO gas is supplied at a flow rate of 2 slminto the first cleaning gas supply pipe 232 h, the FNO is generated inthe first cleaning gas supply pipe 232 h according to a reactionformula: F₂+2NO→2FNO and supplied at a flow rate of 2 slm into theprocessing chamber 201. In this case, the flow rate of the NF₃ gassupplied into the processing chamber 201 via the second cleaning gassupply pipe 232 e is, for example, 2 slm.

The gas containing FNO and the NF₃ gas introduced into the processingchamber 201 are mixed in the processing chamber 201, flow upward in theprocessing chamber 201, flow out through an upper end opening of theinner tube 204 into the cylindrical space 250, flow downward in thecylindrical space 250, and are exhausted through the exhaust pipe 231.While passing through the processing chamber 201, the NF₃ gas contactsthe deposit including the thin film, such as the silicon nitride film,which is accumulated on the inner wall of the process tube 203 or asurface of the boat 217 to remove the thin film by a thermal chemicalreaction. In addition, the FNO serves to accelerate the etching reactionby the NF₃ gas. Accordingly, the FNO-containing gas is mixed with theNF₃ gas in the processing chamber 201 to cause a state where the NF₃ gasand the FNO gas exist together in the processing chamber 201 so that anetching rate by the NF₃ gas can be increased.

Here, the N₂ gas may be supplied from the N₂ gas supply source 273serving as the inert gas supply source into the processing chamber 201so that each of the gas containing the FNO and the NF₃ gas can bediluted with the N₂ gas. For example, by opening the valves 262 c, 261c, 262 d, and 261 d, the N₂ gas supplied from the N₂ gas supply source273 into each of the inert gas supply pipes 232 c and 232 d iscontrolled to a desired flow rate by each of the MFCs 241 c and 241 d,passes through each of the inert gas supply pipes 232 c and 232 d, andis introduced from each of the nozzles 230 a and 230 b into theprocessing chamber 201 via each of the processing gas supply pipes 232 aand 232 b. The N₂ gas is mixed with the NF₃ gas and the FNO-containinggas inside each of the processing gas supply pipes 232 a and 232 b. Theconcentrations of the FNO-containing gas and the NF₃ gas may becontrolled by adjusting the flow rate of the supplied N₂ gas. Also, inaddition to the N₂ gas, a noble gas such as an argon (Ar) gas and ahelium (He) gas may be used to dilute the FNO-containing gas and the NF₃gas.

Meanwhile, the thin film is etched during the cleaning process under thefollowing exemplary conditions:

Temperature in the processing chamber: 200 to 600° C.,

Pressure in the processing chamber: 133 Pa (1 Torr) to 66,500 Pa (500Torr),

Temperature in the preliminary decomposition chamber: 500 to 800° C.,

Pressure in the preliminary decomposition chamber: 133 Pa (1 Torr) toatmospheric pressure (760 Torr),

Supply flow rate of the NF₃ gas: 200 sccm (0.2 slm) to 4,000 sccm (4slm),

Supply flow rate of the NO gas: 200 sccm (0.2 slm) to 4,000 sccm (4slm),

Supply flow rate of the N₂ gas: 500 sccm (0.5 slm) to 20,000 sccm (20slm).

The etching of the thin film is performed by maintaining the respectiveetching conditions constant within the respective ranges.

After a predetermined etching time has elapsed, the etching of theprocessing chamber 201 is terminated by closing the valves 262 e, 261 e,262 f, 261 f, 262 g, and 261 g to stop the supply of the FNO-containinggas and the NF₃ gas into the processing chamber 201. Thereafter, thevalves 262 c, 261 c, 262 d, and 261 d are opened and the inside of theprocessing chamber 201 is purged by supplying the N₂ gas from the N₂ gassupply source 273 into the processing chamber 201 and exhausting the N₂gas through the exhaust pipe 231. An inner atmosphere of the processingchamber 201 is replaced with the N₂ gas to return the inner pressure ofthe processing chamber 201 to an atmospheric pressure, therebyterminating the cleaning process according to the present embodiment.

When the cleaning process is terminated, the seasoning process ofpre-coating the thin film inside the processing chamber 201 isperformed. Thereafter, the above-described thin-film forming process isresumed.

(4) Effects According to the Embodiment

According to the embodiment, one or more following effects are obtained.

According to the embodiment, with the processed wafer 200 dischargedfrom the processing chamber 201, the gas containing FNO generated bypre-mixing the F₂ gas obtained by preliminarily decomposing the NF₃ gasand the NO gas is supplied from the first cleaning gas supply systeminto the processing chamber 201 and the same is exhausted andsimultaneously, the NF₃ gas is supplied from the second cleaning gassupply system installed apart from the first cleaning gas supply systemand the same is exhausted. That is, during the cleaning process, theFNO-containing gas is mixed (post-mixed) with the NF₃ gas to cause astate where the NF₃ gas and the FNO gas exist together in the processingchamber 201. Since the FNO accelerates the etching reaction by the NF₃gas, the etching rate can be increased to improve the cleaningperformance Moreover, by causing a state where the NF₃ gas and the FNOgas exist together in the processing chamber 201, processing conditionssuch as the temperature and the pressure may be adjusted to a lowtemperature and a low pressure. For example, even if the inside of theprocessing chamber 201 is adjusted to a temperature of about 400° C.under a pressure of about 100 Torr, the cleaning process may besufficiently performed. Further, it is confirmed that the etchingprocess is not facilitated due to the low etching rate of the FNO gaswhen only the FNO gas is supplied into the processing chamber 201instead of the mixture of the NF₃ gas and the FNO gas. That is, it hasbeen identified that, the etching process is not facilitated when onlythe FNO gas is used although the FNO gas added to the cleaning gasaccelerates the etching reaction by the cleaning gas.

In addition, according to the embodiment, the NF₃ gas is decomposed intothe F₂ gas and the N₂ gas in the preliminary decomposition chamber 280f, and the F₂ gas is mixed with the NO gas in the first cleaning gassupply pipe 232 h. In other words, in accordance with the embodiment,the F₂ gas and the NO gas are mixed in advance (pre-mixed) with eachother in the first cleaning gas supply pipe 232 h instead of separatelysupplying each of the F₂ gas and the NO gas into the processing chamber201. Thus, by pre-mixing the F₂ gas and the NO gas in the first cleaninggas supply pipe 232 h, the generation efficiency of FNO can be improved.

As described above, according to the embodiment, when the cleaningprocess is performed by adding the NO gas to the gas containing F atoms,the handling can be facilitated, and the controllability of the cleaningperformance can be improved.

In addition, according to the embodiment, the NO gas is used as anoxygen-containing gas to be mixed with the F₂ gas to improve thegeneration efficiency of the FNO. Further, when an N₂O gas or an NO₂ gasis used as the oxygen-containing gas instead of the NO gas, a dedicatedpreliminary decomposition chamber, that is, a preliminary decompositionchamber only for the N₂O gas or the NO₂ gas is required due to a lowreactivity of the N₂O gas and NO₂ gas with the fluorine-containing gas.On the contrary, since the NO gas sufficiently reacts with the F₂ gas inthe first cleaning gas supply pipe 232 h, it is unnecessary to installthe dedicated preliminary decomposition chamber, that is, thepreliminary decomposition chamber only for the NO gas. Furthermore, whenan O₂ gas is used as the oxygen-containing gas instead of the NO gas,FNO is not generated.

In addition, according to the present embodiment, the FNO-containing gasis mixed with the NF₃ gas in the processing chamber 201 to generate themixture of the NF₃ gas and the FNO gas so that the silicon nitride filmcan be etched more than quartz. Thus, damage to the quartz member [theprocess tube 203 and the boat 217, etc.] in the processing chamber 201can be reduced. Moreover, since the FNO gas etches an oxide layer suchas a SiO₂ layer, it is likely that quartz members are corroded by theFNO gas. However, by generating the mixture of the FNO gas and the NF₃gas by mixing the FNO-containing gas with the NF₃ gas in the processingchamber 201, the etching of the silicon nitride layer can befacilitated, the etching of the quartz members can be suppressed, andthe corrosion of the quartz members, namely, the damage to the quartzmembers, can be reduced.

While the present invention has been particularly described withreference to the embodiments thereof, the present invention is notlimited thereto and changes may be made thereto without departing fromthe spirit and the scope of the invention.

For instance, a gas highly reactive to the NO gas, for example, the F₂gas or a chlorine fluoride gas such as a chlorine trifluoride (ClF₃)gas, may be used instead of the NF₃ gas as the gas containing F atoms tobe mixed with the NO gas. In this case, a decomposition source, such asa plasma source or a heater is not required to be installed in thepreliminary decomposition chamber 280 f. In addition, as shown in FIG.3, the preliminary decomposition chamber 280 f is not required to beinstalled in the first cleaning gas supply system. Furthermore, evenwhen the F₂ gas or the ClF₃ gas is used, the decomposition source or thepreliminary decomposition chamber 280 f may be installed, therebyfurther accelerating the decomposition of the fluorine-containing gas.Moreover, by elongating the flow path through which the F₂ gas generatedby the preliminary decomposition or the directly supplied F₂ gas and theNO gas meet each other and flow into the processing chamber 201,reactivity between the gas containing F atoms and the NO gas can befurther increased.

In accordance with the embodiment, the FNO gas may be generated bymixing in advance (pre-mixing) the gas containing F atoms, which ishighly reactive with the NO gas, with the NO gas. In the cleaningprocess, the same effects as in the above-described embodiment can beobtained by generating a mixture of one of the F₂ gas and the ClF₃ gasand the FNO gas in the processing chamber 201.

In addition, the thin film is etched using the F₂ gas as thefluorine-containing gas during the cleaning process under the followingexemplary conditions:

Temperature in the processing chamber: 200 to 500° C.,

Pressure in the processing chamber: 133 Pa (1 Torr) to 66,500 Pa (500Torr),

Supply flow rate of the F₂ gas supply flow rate: 200 sccm (0.2 slm) to4,000 sccm (4 slm),

Supply flow rate the NO gas: 200 sccm (0.2 slm) to 4,000 sccm (4 slm),

Supply flow rate of the N₂ gas: 500 sccm (0.5 slm) to 20,000 sccm (20slm).

In addition, the thin film is etched using the ClF₃ gas as thefluorine-containing gas during the cleaning process under the followingexemplary conditions:

Temperature in the processing chamber: 200 to 500° C.,

Pressure in the processing chamber: 133 Pa (1 Torr) to 66,500 Pa (500Torr),

Supply flow rate of the ClF₃ gas: 200 sccm (0.2 slm) to 2,000 sccm (2slm),

Supply flow rate of the NO gas: 200 sccm (0.2 slm) to 2,000 sccm (2slm),

Supply flow rate of the N₂ gas: 500 sccm (0.5 slm) to 20,000 sccm (20slm).

Since the F₂ gas has a very high reactivity and care is required whenhandling the F₂ gas, charging a cylinder with the gas under a highpressure is impossible in view of safety. Accordingly, a chargingpressure is limited to several bars at maximum in terms of a partialpressure of F₂ gas. For this reason, when the gas is supplied from thecylinder, it is difficult to perform a long cleaning process or to cleana plurality of film-forming apparatuses at the same time. Moreover, afrequent change of the cylinders is required resulting in an increase ina possibility of a gas leakage. While the above-described problem may beavoided by synthesizing the F₂ gas on the spot, highly expensiveaccessory equipment is required, and scrupulous care should be taken toprepare the F₂ gas by electrolyzing a hydrogen fluoride (HF) having ahigh reactivity. Further, the HF may serve to corrode pipes, etc.

In addition, since the ClF₃ has high reactivity and is in a liquid format room temperature and has a very low allowable concentration (criticalvalue) of about 0.1 ppm in an atmosphere, the use of the ClF₃ gas isoutlawed in some countries. Further, since an initial pressure is verylow at room temperature, a supply of a large amount of ClF₃ gas involvesaccelerating an evaporation of the ClF₃ gas by an external heating.Accordingly, high-priced accessory equipment is required. Further, whenthe ClF₃ gas is re-liquefied in the pipes, the pipes may be corroded.

By comparison, while the NF₃ gas is a strong oxidizer, the NF₃ gas isextremely inactive and non-flammable about room temperature. Since theallowable concentration of the NF₃ gas in the atmosphere has a criticalvalue of about 30 ppm, which is much higher than that (1 ppm) of F₂ gas,the NF₃ gas is less toxic than the F₂ gas. In addition, a supply of alarge amount of the NF₃ gas by the cylinder is possible and the largeamount of the NF₃ gas is consumed in recent semiconductor manufacturingprocesses.

As described above, the NF₃ gas is chemically more stable, less toxic,and easier to handle compared to the F₂ gas and the ClF₂ gas. In thisrespect, it can be seen that the above-described embodiment in which theNF₃ gas is used as the fluorine-containing gas is advantageous, forexample, over the other embodiments.

In addition, a perfluorocarbon (PFC) gas, namely, a fluorocarbon gassuch as a CF₄ gas, a C₂F₆ gas, or a C₃F₈ gas may be used instead of theNF₃ gas as the gas containing F atoms to be mixed with the NO gas. Inthis case, the PFC gas is preliminarily decomposed by the decompositionsource such as the plasma source and the heater in the preliminarydecomposition chamber 280 f. Moreover, the PFC gas is more difficult tobe decomposed thermally and is thermally decomposed at a highertemperature compared to the NF₃ gas. Accordingly, the thermaldecomposition of the PFC gas involves applying a heat at a relativelyhigh temperature and is preferably performed using plasma. Preferably,the PFC gas is preliminarily decomposed by the plasma source in thepreliminary decomposition chamber 280 f.

In addition, when the PFC gas (for example, the CF₄ gas) ispreliminarily decomposed to generate the F₂ gas, it is preferable thatO₂ added to prevent the decomposed F₂ gas from reverting back to the CF₄gas. That is, it is preferable that a gas obtained by adding the O₂ tothe CF₄ gas is preliminarily decomposed by the plasma source in thepreliminary decomposition chamber 280 f. Moreover, by elongating theflow path through which the F₂ gas generated by the preliminarydecomposition as in the above-described embodiment and the NO gas meeteach other and flow into the processing chamber 201, reactivity betweenthe gas containing F atoms and the NO gas can be further increased.

In accordance with the embodiment, the gas obtained by preliminarilydecomposing the PFC gas serving as the gas containing F atoms is mixedin advance (pre-mixed) with the NO gas, thereby generating FNO. In thecleaning process, the same effects as in the above-described embodimentcan be obtained by generating a mixture of the PFC gas and the FNO gasin the processing chamber 201.

In addition, the thin film is etched using the CF₄ gas as thefluorine-containing gas during the cleaning process under the followingexemplary conditions:

Temperature in processing chamber: 200 to 600° C.,

Pressure in processing chamber: 133 Pa (1 Torr) to 66,500 Pa (500 Torr),

Supply flow rate of the mixture of the CF₄ gas and the O₂: 200 sccm (0.2slm) to 4,000 sccm (4 slm),

Supply flow rate of the NO gas: 200 sccm (0.2 slm) to 4,000 sccm (4slm),

Supply flow rate of the N₂ gas: 500 sccm (0.5 slm) to 20,000 sccm (20slm).

Furthermore, in the PFC gas, the CF₄ gas and the C₂F₆ gas [aliphatichydrocarbon completely saturated with fluorine] having molecularstructures that are free from double bonds are highly stable gases anddo not easily cause chemical reactions because the CF₄ gas and the C₂F₆gas have at least twice the molecule bonding energy compared to the NF₃gas. However, a difficult point may be that the CF₄ gas and the C₂F₆ gashave very high global warming factors (GWFs) due to their stability.

Hereinafter, preferred embodiments of the present invention will befurther described in detail.

An embodiment of the present invention provides a substrate processingapparatus including:

a processing vessel configured to process a substrate;

a processing gas supply system configured to supply a processing gasinto the processing vessel;

a first cleaning gas supply system configured to supply a pre-mixed gasincluding a fluorine-containing gas and a nitrogen monoxide gas into theprocessing vessel;

a second cleaning gas supply system installed apart from the firstcleaning gas supply system and configured to supply thefluorine-containing gas into the processing vessel; and

a controller configured to control the processing gas supply system, thefirst cleaning gas supply system, and the second cleaning gas supplysystem in a manner that the processing gas is supplied into theprocessing vessel accommodating the substrate to form a thin film on thesubstrate, and that the pre-mixed gas and the fluorine-containing gas issupplied into the processing vessel through the first cleaning gassupply system and the second cleaning gas supply system respectively soas to remove a deposit containing the thin film adhered to an inside ofthe processing vessel.

Another embodiment of the present invention provides a substrateprocessing apparatus including:

a processing vessel configured to process a substrate;

a processing gas supply system configured to supply a processing gasinto the processing vessel;

a first cleaning gas supply system comprising a preliminarydecomposition chamber for decomposing a fluorine-containing gas, thefirst cleaning gas supply system configured to supply a pre-mixed gasincluding a gas obtained from decomposing the fluorine-containing gas inthe preliminary decomposition chamber and a nitrogen monoxide gas intothe processing vessel;

a second cleaning gas supply system installed apart from the firstcleaning gas supply system and configured to supply thefluorine-containing gas into the processing vessel; and

a controller configured to control the processing gas supply system, thefirst cleaning gas supply system, and the second cleaning gas supplysystem in a manner that the processing gas is supplied into theprocessing vessel accommodating the substrate to form a thin film on thesubstrate, and that the pre-mixed gas and the fluorine-containing gas issupplied into the processing vessel through the first cleaning gassupply system and the second cleaning gas supply system respectively soas to remove a deposit containing the thin film adhered to an inside ofthe processing vessel.

Preferably, the pre-mixed gas includes a FNO gas generated by reactionof the fluorine-containing gas and the nitrogen monoxide gas in thefirst cleaning gas supply system.

Preferably, the pre-mixed gas includes a FNO gas generated by reactionof the gas obtained from decomposing the fluorine-containing gas and thenitrogen monoxide gas in the second cleaning gas supply system.

Preferably, the fluorine-containing gas is a fluorine gas or a chlorinefluoride gas.

Preferably, the fluorine-containing gas is a nitrogen fluoride gas or afluorocarbon gas.

Still another embodiment of the present invention provides a method ofmanufacturing a semiconductor device, including:

supplying a processing gas into a processing vessel accommodating asubstrate to form a thin film on the substrate; and

supplying a pre-mixed gas including a fluorine-containing gas and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto an inside of the processing vessel.

Yet another embodiment of the present invention provides a method ofmanufacturing a semiconductor device, including:

supplying a processing gas into a processing vessel accommodating asubstrate to form a thin film on the substrate; and

supplying a pre-mixed gas including a gas obtained from decomposing afluorine-containing gas in a preliminary decomposition chamber and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto an inside of the processing vessel.

Yet another embodiment of the present invention provides method ofcleaning an inside of a processing vessel including:

providing the processing vessel configured to process a substrate toform a thin film thereon; and

supplying a pre-mixed gas including a fluorine-containing gas and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto the inside of the processing vessel.

Yet another embodiment of the present invention provides a method ofcleaning an inside of a processing vessel including:

providing the processing vessel configured to process a substrate toform a thin film thereon; and

supplying a pre-mixed gas including a gas obtained from decomposing afluorine-containing gas in a preliminary decomposition chamber and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto the inside of the processing vessel.

1. A substrate processing apparatus comprising: a processing vesselconfigured to process a substrate; a processing gas supply systemconfigured to supply a processing gas into the processing vessel; afirst cleaning gas supply system configured to supply a pre-mixed gasincluding a fluorine-containing gas and a nitrogen monoxide gas into theprocessing vessel; a second cleaning gas supply system installed apartfrom the first cleaning gas supply system and configured to supply thefluorine-containing gas into the processing vessel; and a controllerconfigured to control the processing gas supply system, the firstcleaning gas supply system, and the second cleaning gas supply system ina manner that the processing gas is supplied into the processing vesselaccommodating the substrate to form a thin film on the substrate, andthat the pre-mixed gas and the fluorine-containing gas is supplied intothe processing vessel through the first cleaning gas supply system andthe second cleaning gas supply system respectively so as to remove adeposit containing the thin film adhered to an inside of the processingvessel.
 2. The substrate processing apparatus of claim 1, wherein thefirst cleaning gas supply system comprises a preliminary decompositionchamber for decomposing the fluorine-containing gas, the first cleaninggas supply system configured to supply a pre-mixed gas including a gasobtained from decomposing the fluorine-containing gas in the preliminarydecomposition chamber and a nitrogen monoxide gas into the processingvessel.
 3. The apparatus of claim 1, wherein the pre-mixed gas comprisesa FNO gas generated by reaction of the fluorine-containing gas and thenitrogen monoxide gas in the first cleaning gas supply system.
 4. Theapparatus of claim 2, wherein the pre-mixed gas comprises a FNO gasgenerated by reaction of the gas obtained from decomposing thefluorine-containing gas and the nitrogen monoxide gas in the secondcleaning gas supply system.
 5. The apparatus of claim 1, wherein thefluorine-containing gas is a fluorine gas or a chlorine fluoride gas. 6.The apparatus of claim 2, wherein the fluorine-containing gas is anitrogen fluoride gas or a fluorocarbon gas.
 7. A method ofmanufacturing a semiconductor device, comprising: supplying a processinggas into a processing vessel accommodating a substrate to form a thinfilm on the substrate; and supplying a pre-mixed gas including afluorine-containing gas and a nitrogen monoxide gas into the processingvessel through a first cleaning gas supply system while simultaneouslysupplying the fluorine-containing gas into the processing vessel througha second cleaning gas supply system installed apart from the firstcleaning gas supply system so as to remove a deposit containing the thinfilm adhered to an inside of the processing vessel.
 8. The method ofclaim 7, wherein the pre-mixed gas includes a gas obtained fromdecomposing the fluorine-containing gas in a preliminary decompositionchamber and a nitrogen monoxide gas.
 9. A method of cleaning an insideof a processing vessel comprising: providing the processing vesselconfigured to process a substrate to form a thin film thereon; andsupplying a pre-mixed gas including a fluorine-containing gas and anitrogen monoxide gas into the processing vessel through a firstcleaning gas supply system while simultaneously supplying thefluorine-containing gas into the processing vessel through a secondcleaning gas supply system installed apart from the first cleaning gassupply system so as to remove a deposit containing the thin film adheredto the inside of the processing vessel.
 10. The method of claim 9,wherein the pre-mixed gas includes a gas obtained from decomposing thefluorine-containing gas in a preliminary decomposition chamber and thenitrogen monoxide gas.